In internal combustion engines having spark ignition of a fuel/air mixture, such as, for example, in the case of reciprocating piston engines or rotary piston engines, at least one spark plug is usually provided for generating an ignition spark. The spark plug for this purpose is secured in a threaded receptacle of a combustion chamber wall, for example, a cylinder head of a reciprocating piston engine. One end of the spark plug projects with electrodes provided at the end into the combustion chamber. Between the electrodes arranged at a defined distance from one another, an ignition spark is generated at a predefined ignition time by applying a high voltage, the ignition spark igniting the fuel/air mixture.
In order to avoid overheating of the spark plug and, in particular, of the electrodes during operation of the internal combustion engine, the spark plug is typically arranged in such a way that the electrodes of the spark plug and therefore the location of the ignition spark are located relatively close to the combustion chamber wall. In this way, only a small portion of the spark plug projects with the electrodes into the combustion chamber, while the by far larger portion is provided within the combustion chamber wall or on the outside thereof. Sufficient cooling of the spark plug is therefore achieved, in particular, by the conduction away of heat into the cooled combustion chamber wall.
However, the inventors herein have recognized potential issues with such systems. As one example, the small distance between the electrodes, and therefore the ignition spark, and the edge of the combustion chamber has a disadvantageous effect on the ignition of the fuel/air mixture in the case of a cold start or during a warming phase of the internal combustion engine. An ignition process, which is unsuitable for the warming-up phase of the internal combustion engine, can bring about, for example, incomplete combustion of the fuel/air mixture. This may give rise to increased fuel consumption and emission of pollutants in the case of a cold start of the internal combustion engine. In one example, the issues described above may be addressed by an internal combustion engine having at least one combustion chamber for burning a fuel mixture and a spark plug for performing spark ignition of the fuel mixture in the combustion chamber, the spark plug having electrodes for generating an ignition spark at a location within the combustion chamber. The internal combustion engine may include one or more cylinders, each cylinder with a corresponding combustion chamber and, in each case, at least one spark plug for each cylinder. Each spark plug is provided in a spark plug receptacle for the corresponding combustion chamber. The spark plug receptacle may be arranged, for example, in a housing surrounding the corresponding combustion chamber, such as, for example, in a cylinder head, in such a way that the spark plug which is secured by the spark plug receptacle projects with a first end including electrodes into the combustion chamber.
In a further example, an internal combustion engine may include an adjustment device for reducing a distance between the location of the ignition spark and an edge of the combustion chamber in the case of an increase in temperature of the internal combustion engine during operation. In particular, a constant electrode distance between the electrodes during a change in the distance of the ignition spark from the edge of the combustion chamber is provided. The location of the ignition spark is, for example, the center point of the electrode spacing or a location of the ignition spark in the case of an electrode. The distance is preferably reduced with respect to an edge of the combustion chamber directly next to the spark plug. The edge of the combustion chamber is defined, by example, by an inner surface of a housing surrounding the combustion chamber. In this context, displacement of the spark plug in its entirety relative to the edge of the combustion chamber or relative to a housing surrounding the combustion chamber can be provided. According to one embodiment, an adjustment device is provided for each spark plug of the internal combustion engine.
Thus, in the case of heating of the internal combustion engine, the location of the ignition spark, defined by the electrodes of the spark plug, in the combustion chamber is shifted by means of the adjustment device from a position located more within the combustion chamber to a position located closer to the edge. Correspondingly, a change in the ignition spark position can occur from a position located closer to the edge to a position located further inside the combustion chamber, and therefore the distance from the edge of the combustion chamber can be increased in the case of cooling of the internal combustion engine. Therefore, in during a cold start of the internal combustion engine the location of the ignition spark is at a larger distance from the edge of the combustion chamber than in an operationally warm state.
In this way, during a warming-up phase of the internal combustion engine significantly more effective ignition and therefore combustion of the fuel/air mixture takes place in the combustion chamber. This gives rise to lower fuel consumption and emission of pollutants in the case of a cold start. When a predefined operating temperature is reached, the location of the ignition spark is set to be closer to the edge of the combustion chamber. In addition to effective ignition of fuel/air mixture, this ensures, in particular, sufficient cooling of the spark plug even in the case of full load. The service life of the spark plug is optimized.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.